Economic incentives for abandoning or expanding gum arabic production in Sudan

In this paper we use a real options approach to analyze farmers' economic incentives to abandon gum production or expand by creating new plantations. Our results indicate that agricultural crops currently provide higher economic benefits as compared to gum agroforestry. However, we show that the incentives for gum producers to abandon gum production is low, because (i) land is abundant, (ii) gum arabic is produced during the dry season and agricultural crops mainly during the wet season, and (iii) the dry season opportunity cost of labor is low. Hence, an increase in deforestation in the near future is not expected. The analysis further shows that an increase in the prices of gum arabic of about 315% is needed to induce an expansion of gum agroforestry and a shift in land use system from continuous agricultural production to gum agroforestry system. Hence, also an expansion of gum forests and/or agroforests in the near future is not expected. Price policies to improve incentives for expanding gum forests are discussed.     

Acacia albida and other multipurpose trees on the fur farmlands in the Jebel Marra highlands,Western Darfur,Sudan

This paper describes the traditional agroforestry systems based on Acacia albida and other multipurpose trees as practised by the sedentary Fur people on the lower slopes and highlands of the Jebel Marra massif, Sudan. The basic agrosilvopastoral system consists of terraced village fields, where semipermanent rainfed cropping of staple millet and other subsistence crops takes place under stands of multipurpose trees dominated by Acacia albida, Cordia abyssinica and Ziziphus spina-christi. Trees have been retained primarily for food, wood and fodder. Thorn from cut and browsed branches makes a good fencing materal.This system has been able to sustain self-sufficiency of a densely settled population over centuries. However, recent out-migration of people from the montane dry-farming areas has caused gradual return to shifting cultivation. As a consequence, the present-day subsistence farming in the region is characterized by a general level of carelessness and exploitative management and this is reflected in a successive decrease of the tree cover.The evaluation of the AF practices described includes a discussion on their regional importance and extrapolability within the framework of similar situations, especially in Africa, emphasis being given to mountain and highland conditions. The outstanding potential for Acacia albida-based AF systems to be sustained and spread almost all over semiarid to semihumid Africa is highlighted by illustrating its ecologic and economic variability. Extrapolation of such examples, however, is not feasible, without thorough feasibility studies concerning the ecologic, ethnologic and socio- economic conditions in the respective project areas. Basic research needs for improving and extending the system are also indicated.     

草鱼肠道微生物对食物改变适应性变化的研究

对草鱼(Ctenopharyngodon idellus)先饲喂人工饲料再饲喂苏丹草,运用PCR-DGGE的方法,比较了食物改变引起的草鱼肠道微生物菌群结构的变化过程。结果显示,饲喂同种饲料的草鱼后肠与前、中肠样品间菌群结构存在显著差异(TH0-F0=-2.268,P0.05;TH0-M0=-2.470,P0.05),饲喂不同种食物的相同肠段样品间菌群结构也存在着显著差异(P0.05)。微生物多样性指数显示,后肠样品Shannon指数H'一般不低于4.25,而前、中肠样品H'均未超过4.25。对后肠样品进一步研究发现,食物改变11 d之后,后肠微生物菌群基本达到稳定。结果表明,草鱼肠道不同部位内容物菌群结构不同,后肠样品具有更高的微生物多样性,并且食物的改变会对草鱼肠道微生物菌群产生快速而显著的影响。     

产油微生物的筛选及其产油率测定

为寻求可再生、环境友好且经济可行的化石能源替代燃料,采用苏丹黑B和尼罗红染色法及甲醇-氯仿提取法对平顶山各地不同生境富含油脂土壤中的高产油脂微生物进行分离筛选。结果表明:试验分离到2株产油菌株PDS1和PDS2。其中,产油细菌PDS1为革兰氏阴性菌,产油率为29.47%;产油细菌PDS2为革兰氏阳性菌,产油率为23.57%。     

凝胶渗透色谱净化-HPLC同时检测麻油中苏丹红Ⅰ-Ⅳ

采用LabTech PrepElite GV全自动凝胶渗透色谱净化-定量浓缩系统对麻油样品进行净化并采用HPLC分析其中的苏丹红Ⅰ-Ⅳ,回收率在93.1%～107.7%,RSD不大于3.7%,该方法灵敏可靠,适合于麻油中苏丹红Ⅰ-Ⅳ的同时检测。      

Yield,N Uptake and N Utilization of Early Maturing,Drought and Striga-Tolerant Maize Varieties under Low N Conditions

Performance under sub-optimal nitrogen (N) conditions, of early maturing maize cultivars bred for tolerance to drought and Striga parasitism in the Nigerian savanna is not known. This study evaluated the tolerance of selected early maturing drought and Striga-tolerant maize cultivars to low N conditions in Northern Nigeria. The cultivars were evaluated at 30 and 100 kg N ha^?1. The varieties were compared with an improved maize cultivar that is not tolerant to drought and Striga. Maize grain yield was 26% higher at 100 kg N ha^?1 than at 30 kg N ha^?1 in 2010 and 161% higher100 kg Nha^?1 than at 30 kg Nha^?1 in 2011. The drought and Striga-tolerant varieties produced consistently higher yields than the non-drought-tolerant variety particularly at 30 kg Nha^?1. These cultivars also accumulated higher amount of N, had higher N-uptake efficiency or N-utilization efficiency than the non-drought-tolerant variety ACR 95 TZE-COMP4 C3. Grains yield at low nitrogen rate was associated with high ears m^?2, high dry matter accumulation, high grains m^?2, suggesting that these traits are linked to low-N tolerance. The good performance of the drought-tolerant maize varieties under low N suggests that varieties developed for drought tolerance may be tolerant to low-N conditions.     

苏丹Ⅲ在有机溶剂中的光催化降解研究

苏丹Ⅲ作为一种偶氮染料不溶于水,微溶于乙醇,易溶于氯仿、油脂、矿物油、丙酮和苯等,属于难挥发、难生物降解性有机物。以纳米TiO2为催化剂,考察了苏丹Ⅲ在3种不同光源2种不同溶剂条件下的光催化降解,讨论了光源种类、溶剂体系和催化剂时间对其降解的影响,并利用紫外吸收光谱等和质谱的手段,考察了苏丹Ⅲ的光解动态和光解产物。结果表明,苏丹Ⅲ的光催化降解符合一级动力学方程,在乙醇溶液中的光解半衰期为58 min,在三氯甲烷/乙醇中的半衰期约为17.2 min。     

聚羟基烷酸合成菌的分离·鉴定及其生长特性研究

［目的］获取性状优良的聚羟基烷酸（PHAs）合成菌。［方法］以东湖底泥、山坡裸地土、肥沃菜园土和油脂浸润土为初始样品,经富集、分离纯化、苏丹黑B染色、红外光谱及气相色谱定性定量分析筛选出具PHAs合成能力的细菌菌株。［结果］苏丹黑B染色结果表明,在分离出的12株细菌中有3株细菌具有PHAs合成能力,其编号分别是Zj5、Zj8和Zj9。3株细菌均在1 741 cm-1附近呈现吸收峰,菌株Zj8和Zj9的红外谱图相似。菌株Zj5、Zj8和Zj9的PHAs含量分别为146.85、0.65和3.48 mg/L,菌株Zj5被初步鉴定为假单胞菌属细菌。菌株Zj5在pH值为5.0-9.0的环境中均能生长,其生长的最适pH值为7.6;在25-35 ℃下均能正常生长,其最适培养温度和通气量分别为30 ℃和100 ml。［结论］ 菌株Zj5、Zj8和Zj9有PHAs合成能力且菌株Zj5的合成能力最强。     

Importance of forest buffers for preserving soil carbon and nutrient stocks in farmed landscapes along two river sites in the savannas of the Volta basin,Ghana

Understanding the impacts of agricultural land use is desired for proper management of riparian forests buffers (RFs) in savannas. In this light, we analyzed the relationship between woody plant diversity and soil properties of RFs in farmlands (FAs) and protected areas (PAs) along Afram (Guinean zone) and Tankwidi (Sudanian zone) Rivers located within the Volta sub-basin of Ghana. ALOS-AVNIR imageries were used to map RFs to facilitate sampling of soil and woody vegetation (dbh ≥5?cm) using stratified randomized design (72 plots; size: 500?m² each) for the analysis of soil physical and chemical properties and Shannon-Wiener plant species diversity. Although the fractions of sand, silt, and clay varied between the PAs and FAs, they were predominantly categorized as sandy loam. Along the Afram River, there were no significant differences in the concentrations and nutrient stocks of soil C, N, P, and K as well as the pH, moisture content, and bulk density between PA and FA. For the Tankwidi River, the concentrations and nutrient stocks of C and K significantly decreased from PA to FA while N, P, pH, bulk density, and moisture content were not different. Of the soil attributes measured C, N, P, pH, ground slope, and soil moisture had significant relationships with the diversity and density of the riparian woody plants. Controlling agricultural activities in riparian forests could preserve soil properties similar to that found in protected areas.